A few years ago, A. Dall'Aglio and A. Porretta showed in [1]} that weak solutions are \(\frac{\gamma -2}{\gamma -1}\) -Hölder continuous, provided that \(f \in L^q\)  and
\(q = q_0 := \frac{N}{\gamma ^{\prime }}=N \frac{\gamma -1}{\gamma }.\) 
